The conventional incandescent lamps have been widely used. However, the conventional lighting devices suffer certain disadvantages, including high power consumption, which leads to wasting of energy, high heat generation, which may cause burning or damage to surrounding articles and objects, short lifespan, which requires frequent replacement and maintenance, and monotonous outer contours, which lacks sense of art.
Recently, with the costs of raw material increasingly raised and shortage of energy, to reduce waste of energy, the lighting industry are developing power-saving lighting bulb to replace the conventional incandescent bulbs. Further due to the drawback of high heat generation of the conventional incandescent bulbs that causes burning and damage of surrounding articles and objects, the power-saving bulbs are rapidly replacing the incandescent bulbs and become the main stream in the market of lighting instruments. Among the known power-saving lighting devices, light-emitting diodes (LEDs) are now under the quick improvement in luminance and are now widely used in various applications.
However, the lighting offered by the LEDs is subjected to constraint of directionality. The LEDs that are currently available in the market can be roughly divided as three categories, the first being one that is of high directionality and has an angular range of illumination less than 20 degrees, the second being one that is of a standard type and has an angular range of illumination between 20 and 45 degrees, and the third being one that is a diffusive type and has an angular range of illumination greater than 45 degrees. All these LEDs, even the diffusive type, are subjected to a certain extent of limitation in the illumination of light thereof. Thus, to apply LEDs to lighting of various applications without being subjected to such a constraint in the angular range of illumination is now one of the major challenges of the industry.
Thus, the present invention aims to provide a light bulb that offers a reasonable design and effectively overcomes the problems associated with the angular range of illumination.